This invention relates to a mobile communication technology and particularly to a technology for controlling channel connections between mobile terminals and wireless base stations.
In a mobile communication system, a mobile terminal receives radio waves from a plurality of surrounding wireless base stations, and selects one of them with the greatest radio field strength to establish a wireless channel connection. So, when a number of mobile terminal users gather around one wireless base station, wireless accesses from the mobile terminal users concentrate in the wireless base station, resulting in degrading communication quality of individual wireless channels. When such a problem happens, each carrier normally adds new wireless base stations to respond to the problems.
As a prior art document on a channel connection technology in the mobile communication system, a patent document JP-A-2007-318295 is cited. The wireless communication system of JP-A-2007-318295 comprises a control station connecting to a plurality of wireless base stations and mobile stations performing wireless communication with the wireless base stations. In the system of JP-A-2007-318295, a mobile station receives an idle signal representing idle channels from the control station, detects the idle channels and selects the detected idle channels to make a wireless channel connection. The idle signal includes information on idle up and down channels, and the mobile station selects an up channel and a down channel of good quality based on the information on the idle up channels and down channels, respectively.
Since degrading communication quality causes users to feel stresses, there need to be some solutions to avoid the channel congestion of the wireless base stations. One of the solutions, adding wireless base stations, requires a large cost and cannot be said to be an efficient solution where the channel congestion is temporary. In the case where a temporary congestion occurs, it is necessary to solve the congestion only then it occurs. It is also desired that the congestion can be predicted and avoided in advance but not after it has occurred.
A method for selecting a channel of good quality may be used in the wireless communication system of JP-A-2007-318295, as the method for avoiding the channel congestion. This method selects a wireless base station for up and down channels only based on the information on idle channels. In the case where the mobile station moves in a direction opposite to the selected wireless base station, the communication is disrupted.
Further, since power consumption is an important performance indicator for a mobile terminal such as a cell phone, it is not desirable from the viewpoint of power consumption that the mobile terminal moves away from the wireless base station to which the mobile terminal is connected via the up channels.
Further, since a mobile station selects the wireless base station to which the mobile station is connected in the method of JP-A-2007-318295, the method cannot be implemented using the existing mobile stations. To realize the method of JP-A-2007-318295, it is necessary for all mobile stations owned by the users to have an additional function.
This invention has been accomplished to solve these problems, and it is an object of this invention to predict that the temporary congestion occurs and to avoid it in advance without adding new wireless base stations.
It is also an object of this invention to avoid the channel congestion taking into consideration the mobility of mobile terminals.